I need everyone's input. I am in sales and marketing for a PCB shop. I need to know by a vote from any CM's why my CM does not like Immersion White Tin and my other resources have no problems or complaints using white tin. Every time an issue comes up we get fingers pointed directly to our white tin. Why is that? We do a lot of white tin for our customers and we get very good reviews on white tin and one so bad, that they want us to switch to immersion Gold. Please Help.
The CM in question has probably seen too many solder problems with White Tin in the past. We have had the same issues.
To save us from spending too much time and money(verifying pure Tin plating thickness, Chemical leaching from the solder mask, improper storage and handling), we have converted our White Tin products over to Immersion Silver. Although some suppliers had consistently good product, we did not want to spend any additional time testing all of them. The switch to ImmAg was easier.
I have to agree with Jax. We've had some successes, and some horrible failures using white-tin. Generally in solderability, and apparently related to the somewhat more rapid deterioration of white-tin finishes.
We've run white-tin as an SMT only assembly, and when run off the shelf, have experienced poor solderability, that looks like it's caused by contaminated pads. Washing these same boards with isopropyl alchohol prior to assembly yields acceptable results.
We've also run white-tin on through hole only boards, with a much lower success rate. Soldering on a solder pot with white-tin finish produced an inordinantly high quantity of blow holes/pin-holes in our assembly. Those same boards run as ENIG boards produced much better results.
Our solution...always request ENIG finish on lead-free assemblies. As a CM, it's easier in general to develop one process that you know works, rather than mess around with processes that are questionable.
And, in response to why the board house gets blamed...well, as with any other element of the supply chain, when there's a problem, root cause needs to be examined. When, as Jax said, the root seems to be solder finish, and seems to be corrected by changing from white-tin to ENIG...well, then the corrective action becomes ENIG...for all like-elements...and that's regardless of the real issue, since the issue has been fixed by changing the board finish, why look any deeper.
I am a CM, We do not use White tin either, we have had numerous solderability issues with this finish, We all agree when done correctly it is good, however I am at about 10% correct and 90% have issues. We currently use Immersion silver and Gold for ourr RoHS PCBAs
I think white tin is fine for a single sided no-clean SMT process but no others.
It's nice that you seek a broader opinion than your own. Further, if we were your customer, we would neither care about the opinions of your other customers nor the observations of a bunch of twitchy CM engineers that you recruited from the internet. If we tried your product and it didn't work as we expected, then it's up to you to help us make it work. Contact Steve Wentz or whoevah at your supplier and get them to help you.
We prefer immersion silver for 20 thou pitch and lower. ENIG is too risky, because fabs and their suppliers don't know how to turn it on and to turn it off.
Thank you for all your help. I help all my customers to understand more about the production of their parts. I even build free parts using 3-4 different finishes so they can evaluate the parts. In working with CM's many of them are always asking us to make the switch from Immersion white tin to ENIG, but when you have a customer that is accustomed to using white tin on all their parts, what could you do. Our CM lost out on many of their projects to another CM that has no problem assembling with white tin. I just don't think that when a customer asks for a certain finish, I myself as the Fabricator/Sales should not try to influence different finishes in order to accommodate my CM. Now I notice no one here likes white tin, can a CM with good knowledge of white tin please say some positives about white tin.